1. Field of the invention
The present invention is directed to a method of fabricating a porous clay composite including inorganic particles with fine metal particles deposited thereon which comprises depositing the metal particles, by irradiation of a light such as ultraviolet light, substantially only on the inorganic particles having photo semiconducting property which are intercalated between layers of an expandable clay.
2. Description of the Prior Art
It is known that inorganic compound particles are intercalated between layers of an expandable clay by an ion-exchange procedure as described in Journal of materials Science 27 (1992) 1297-1301. That is, the expandable clay such as Na-montmorillonite is expanded with a solvent, for example, water, for obtaining an expanded clay. The clay also has a number of hydrated exchangeable cations located between the layers. On the other hand, a sol solution including the inorganic compound particles is prepared, and then mixed with the expanded clay. Since the exchangeable cations in the clay are substituted with the inorganic compound particles having positive charges in the mixed sol solution, the inorganic compound particles are intercalated between the layers of the clay. After the intercalating, the mixed sol solution is dried by a supercritical drying, so that an inorganic compound particles-intercalated clay is obtained without disrupting a porous structure thereof. By the way, it is considered for obtaining an excellent oxidation/reduction catalyst that fine metal particles having oxidation/reduction catalysis are uniformly dispersed in the inorganic compound particles-intercalated clay so as to have a large total surface area of the metal particles. In a past, an impregnation method and a precipitation method were performed to disperse the metal particles in the inorganic compound particles-intercalated clay. For example, in accordance with the impregnation method, the inorganic compound particles intercalated clay is crushed to form powders thereof. A solution including metal ions is added to the powders little by little, and then the solution including the metal ions and the powders is agitated, so that the fine metal particles are formed on the powders. However, the metal particles were formed on the inorganic compound particles intercalated between the layers, and also on the layers of the expanded clay according to the impregnation method. The metal particles formed on the layers of the expanded clay can not function as the oxidation/reduction catalyst. Moreover, as the metal particles having a relatively large size are formed on the inorganic compound particles, it is not easy to obtain the large total surface area of the metal particles. Therefore, oxidation/reduction catalysis of the obtained metal particles will not be enough. Similarly, there are the same problems with respect to metal particles formed in accordance with the precipitation method.